1. Field of the Invention
The present invention is directed to methods and devices for testing for seal integrity in containers and packages which include flexible or semi-flexible gas permeable materials. More specifically, the invention is directed to testing for leaks in seals of such containers by methods and devices which specifically monitor absolute and differential pressures within a vacuum chamber in which a product package or container is seated during a testing cycle.
2. Brief Description of the Related Art
There is an ever increasing need to ensure for product integrity of packaged goods including sterile medical packages, pharmaceuticals and the like to protect persons the products are used on from possible infection by contaminated products. Often, the type of testing required relates directly to the type of packaging or container in which a product is housed. Testing of products which are packaged in generally non-flexible containers, such as cans, are generally tested by procedures which do not apply to testing of products in flexible containers such as pouches or covered trays.
Over the years there have been numerous innovations made for developing methods and devices for testing the integrity of seals associated with flexible walled packages or trays having flexible closures. Testing procedures have included the use of devices for applying pressure to packages which are carried along a conveyor in which the amount of deflection of the packages, or the amount of recovery, are measured in an effort to determine whether or not leaks are present either in the packaging materials or in the seals associated therewith. Other types of leak testers incorporate vacuum sources wherein packages are placed within chambers and vacuums applied to create differential pressures between the interiors of the packages and the surrounding chambers. Pressures within the testing chambers can be monitored so as to determine if there are changes in pressure after vacuums or partial vacuums are applied to create the pressure differentials and thereby give indications of leaks.
In U.S. Patent 5,513,516 to Stauffer, a method and apparatus for testing of containers is disclosed which incorporates a vacuum chamber in which a flexible or semi-flexible package is cooperatively received. A flexible wall or membrane is provided within the testing chamber and is designed to provide a sealing surface against a flexible wall of a container. Such a device was an improvement over the prior art as the use of the flexible wall or membrane allowed package materials formed of gas permeable materials to be sealed during the testing process.
In the testing of packages which include gas permeable materials, it is important that the gas permeable materials not be allowed to communicate with a vacuum area of a testing chamber, unless pin holes in the Tyvek(trademark) lid have to be detected. The amount of leakage through the gas permeable materials may vary depending upon the exact gas permeable material being used such that consistency of test results can not be verified or compared from one package to another due to the difference in leakage rates through the gas permeable materials when vacuums are drawn to create differential pressures between the interiors and exteriors of the packages under test. In the patent to Stauffer, the flexible wall or membrane is designed to close off the gas permeable material at the initiation of a test procedure such that the membrane is drawn into close proximity with the gas permeable material by the application of a vacuum or partial vacuum thus sealing the material from the remaining portion of the package or container under test.
The application of a vacuum in the area of a package seal results in the flexible membrane compressing the area of the seal with the amount of compression increasing depending upon the vacuum being applied. By regulating the pressure along the seal, with the level of vacuum it becomes a medium by which certain seal defects can be detected more or less, depending on the customer""s test criteria.
In U.S. Patent 6,050,133 to Achter et al., a method and apparatus for detecting leaks in packages is disclosed which includes an apparatus and method for testing packages overcoming the aforementioned xe2x80x9cclaimedxe2x80x9d shortcomings. In this patent, a temporary barrier is applied to the gas permeable portion of the sealed package with the exception of a small aperture area through which a tracer gas may be supplied through the gas permeable portion and into the interior of the package. The temporary barrier is formed of an adhesive backed material which is applied to the gas permeable material to seal the material. By measuring the concentration of tracer gas outside of the seal of a package within a test chamber, it is possible to determine whether or not a leak exists in the seal of the package or container.
Unfortunately, this type of testing apparatus and method is a very tedious and slow procedure requiring application of an adhesive material to seal the gas permeable material of the package. Not only must the adhesive layer be applied, it must also be removed after the package has been tested. This is labor intensive and time consuming. Also, the adhesive material can adversely effect printing on the package or may even result in failure of a portion of the package including the gas permeable layer or the seal layer upon the removal of the adhesive covering material from the package.
One of the essential features of any testing method and apparatus is that it must be economical to the manufacturer to use so that cost of products are not increased due to slow testing procedures. When it becomes necessary to apply adhesive coverings to packages to be tested, the amount of time required for a test is increased significantly and, therefore, such procedures are not well suited for mass commercial uses wherein continuous testing of package products must be accomplished in an expeditious manner under very high speed packaging conditions.
In view of the foregoing, there remains a need to provide an apparatus and procedures for testing packages which incorporate gas permeable materials in order to ensure that the seals associated with such packages are intact and do not contain leaks which can effect the quality of the product contained within the packages but wherein such tests can be done expeditiously so as not to adversely effect the overall economics of the packaging procedures.
The present invention is directed to a method and apparatus for leak testing of packages and containers which include at least one surface layer formed of a gas permeable material such that gas is allowed to pass into and out of an interior space of the packages. The apparatus includes a vacuum testing chamber formed by opposing tool components one of which normally would form a bottom component and the other a top component, however, different orientations may be possible and yet remain within the teachings of the invention. The two components form therebetween a testing chamber in which a package to be tested is inserted such that the edges thereof which are sealed extend outwardly of the chamber between flanges of the opposing tools.
In a first embodiment, a package such as a tray or other container having one or more product containing pockets which are sealed by one or more gas permeable materials is initially positioned within one of the opposing tools with the seals surrounding the tray extending outwardly along the flanges of the opposing tools. A flexible bladder, preferably formed of a soft silicon rubber type material, but not limited thereto, is placed in overlying relationship with respect to the gas permeable material and extends outwardly, in some embodiments, beyond seals which are provided between the flanges of the opposing tools forming the test cavity. The seals associated with the test cavity are positioned exteriorly or outwardly beyond the seals of the package under test. In a preferred embodiment of the invention, a foam material, which is contoured to the outer contour of the package as it is initially formed, is provided along the opposite surface of the flexible bladder and is pressed against the bladder. The foam presses the bladder against the gas permeable material in such a manner as to not compress the material but to ensure that the gas permeable material is sealed by the flexible bladder and in such a manner that the seal of the package under test is not effected by the placement of the bladder in sealing relationship with respect to the gas permeable layer of the package.
The foam may be carried by a movable tool member of the test cavity such that the foam and bladder are applied to the package at the time the vacuum chamber is closed.
A pressure testing system such as that disclosed in U.S. Pat. No. 5,513,516 communicates with an evacuation area surrounding the seal between the gas permeable material and the tray of the package. The evacuation area includes an area surrounding the package such that the seal is in open communication with a channel through which gas may pass to the pressure testing system to thereby provide a determination of pressure differential or absolute pressure measurements which can be used to determine whether or not a leak exists in the seal of the package under test.
During a test, a source of vacuum is connected with the gas channel from the test chamber such that at least a partial vacuum may be applied in the area of the seals of the package under test to thereby create a differential pressure between the pressure within the interior of the package and the pressure surrounding the seal. Should a leak exist, gas will pass through the seal and can be detected by changes in pressure being monitored once the at least a partial vacuum has been applied.
From the foregoing, the tools forming the test chamber provide a seal exteriorly of the seal of the package with the area of communication to the test system being created intermediate such seals. In this manner, the exterior seals can be constructed so as to ensure that there is no gas leakage therebetween without any adverse compressive forces applied to the seal of a package under test.
In some embodiments, the foam material which backs the flexible bladder will extend outwardly above at least a portion of the seal of the package. In this manner, there will be less tendency of the reduced pressure within the area surrounding the seal of the package under test causing the flexible bladder to further compress the package seal.
In another embodiment of the invention, packages which include opposing gas permeable layers, such as flexible pouches, are tested in a test chamber having a pair of opposing flexible bladders or membranes which are each backed by a foam material contoured to match the contour of the package prior to test. In this embodiment, the edges of the package defining the seal(s) are situated between generally fixed flanged areas of the opposing tools of the test cavity. A package placed in the test chamber is retained by the closure of the tool components relative to one another with the foam layers ensuring that the opposing flexible bladders seal off the gas permeable layers of the packaging material before any vacuum is applied to the area surrounding the seals of the package under test. The method of testing incorporates the same pressure monitoring system as previously described.
In the preferred embodiments described, the foam material is a somewhat flexible or soft foam material, however, the resilience of the foam material may vary, being somewhat more flexible towards the center and more rigid towards the side edges of the package under test.
In alternative embodiments of the invention, as opposed to using the foam material for backing the flexible bladders or membranes, a positive pressure may be applied by introducing a gas, liquid or other fluid into the area behind the bladders and causing the bladders to thus conform to the outer configuration of the package under test before a vacuum or partial vacuum is applied to the areas of the seal associated with the package. In this manner, forces are applied to conform the flexible bladders to the original configuration of the outer gas permeable walls of the package under test using a fluid as opposed to a solid.
In a further embodiment of the invention, adjustable seals may be associated with the test apparatus. Such seals include inflatable bladders or other materials for increasing the pressure compressing the seals of the package under test. Under such conditions, it is necessary to determine a relationship between the amount of pressure applied at the area of the seal and degree of leakage being measured by the pressure testing or sensing system of the invention, as increased pressure at the seals would reduce the amount of leakage detected by the test system.
The apparatus and systems of the present invention may also be utilized to test the integrity of the materials which form the packages and containers being tested and particularly for testing the gas permeable materials associated with such packages. In some instances, small pin-type holes may exist in such packaging layers which openings can be detrimental to the integrity of the packages and the sterility of the contents thereof. In this respect, the flexible bladders used with the various embodiments of the invention may be provided with a contoured or roughen lower surface which engages the gas permeable material of the packages or containers during testing. Such roughened or contoured surfaces provide a plurality of vent areas by way of which gas can pass to the cavity or chamber under a vacuum test. By monitoring the pressures an immediate indication of holes in the gas permeable material may be easily detected when compared with predetermined pressures associated with known gas permeable materials.
It is the primary object of the present invention to provide a method and apparatus for accurately testing for leaks in seals of packaging which incorporate gas permeable layers, either in a tray type form having a gas permeable cover or in a pouch type form wherein opposing gas permeable layers are sealed at their edges to one another, to ensure that product integrity is maintained and that any material retained within the package is safe for its intended use.
It is also an object of the invention to provide a method and apparatus for testing packaging to ensure integrity of seals wherein the system allows for substantially continuous testing of products such that a products under test can be tested within a matter of one to three seconds without requiring any modification to the package to initiate the tests as is the case with some prior art methods and devices for integrity testing of seals.
It is yet another object of the invention to provide a method and apparatus for testing gas permeable flexible wall containers wherein pressure decay technology is utilized to determine leaks without requiring the injection of costly tracer gases into packaged products.
It is also an object of the invention to provided method and apparatus for testing gas permeable flexible wall containers wherein the integrity of the gas permeable material may also be tested to ensure that no adversely large openings or holes exist therein which could comprise the sterility of contents of the containers.